VSC-MTDC故障特征分析与保护策略研究

发布时间：2018-06-17 23:37

本文选题：多端柔性直流输电 + 直流侧故障分析　；参考：《华北电力大学》2014年硕士论文

【摘要】：多端柔性直流输电系统(Multi-terminal DC Transmission System based onVSC，VSC-MTDC)因其运行方式灵活、可靠等诸多优势，在分布式发电系统并网、新能源发电并网、城市高压直流配电等领域拥有广阔应用前景，是未来直流输电技术的重要发展方向。本文采用理论分析与仿真验证相结合的方法，以多端柔性直流输电控制策略、直流侧故障特征分析以及直流侧故障后的保护策略为核心展开研究。首先，本文分析比较了多端柔性直流系统的接线方式，以及两电平电压源换流器、三电平二极管中性点钳位型电压源换流器以及模块化多电平换流器这三种应用较为广泛的换流器拓扑结构。在推导出多端柔性直流输电系统数学模型的基础之上，结合多端柔性直流输电的应用场合，针对所连不同交流系统设计了满足其稳定运行的单个柔性直流换流站站级控制策略。然后，为了提出具有针对性的直流侧故障保护策略，本文分析了多端柔性直流系统的直流侧正负极间短路故障、单极接地故障、断线故障的故障特征。根据换流器拓扑结构的不同，分两大类进行了理论分析，并且在PSCAD/EMTDC软件中进行了仿真分析。最后，论文在分析了多端柔性直流系统直流线路保护发展的趋势以及现有直流线路保护策略缺陷的基础上，提出了基于小波分析的直流输电线路边界保护算法，并且在PSCAD/EMTDC环境下搭建了一个四端网状多端直流系统模型，，仿真数据通过Matlab小波分析包进行处理。仿真结果表明论文所提出的基于小波分析的直流线路边界保护算法能够实现多端直流系统直流侧故障保护的选择性及速动性。论文针对多端柔性直流输电系统直流侧故障所提出的保护策略能够实现系统故障后的快速恢复，有效地提高了多端系统的故障穿越能力。
[Abstract]:Multi-terminal DC Transmission system based on VSC-MTDC (Multi-terminal DC Transmission system based on VSC-MTDC) has a broad application prospect in distributed generation system, new energy generation, urban HVDC distribution and so on because of its flexible and reliable operation. It is an important development direction of DC transmission technology in the future. In this paper, the control strategy of multi-terminal flexible direct current transmission, the characteristic analysis of DC side fault and the protection strategy after DC side fault are studied by combining theoretical analysis and simulation verification. Firstly, the connection mode of multi-terminal flexible DC system and the two-level voltage source converter are analyzed and compared. Three-level diode neutral clamping voltage source converter and modularized multilevel converter are three widely used converter topologies. Based on the mathematical model of multi-terminal flexible direct current transmission system, combined with the application of multi-terminal flexible direct current transmission system, a single flexible DC converter station level control strategy is designed for different AC systems connected to meet its stable operation. Then, in order to put forward the strategy of DC side fault protection, the fault characteristics of DC side positive and negative pole short circuit fault, single pole grounding fault and break line fault of multi-terminal flexible DC system are analyzed in this paper. According to the different topology structure of the converter, the theoretical analysis is carried out in two categories, and the simulation analysis is carried out in PSCAD / EMTDC software. Finally, on the basis of analyzing the development trend of DC line protection in multi-terminal flexible DC system and the shortcomings of existing DC line protection strategy, a wavelet analysis based DC transmission line boundary protection algorithm is proposed. A four-terminal mesh multi-terminal DC system model is built in PSCAD / EMTDC environment. The simulation data is processed by Matlab wavelet analysis package. The simulation results show that the proposed DC line boundary protection algorithm based on wavelet analysis can realize the selectivity and rapidity of DC side fault protection in multi-terminal DC system. In this paper, the proposed protection strategy for DC side faults of multi-terminal flexible direct current transmission system can achieve fast recovery after system failure, and effectively improve the fault traversing ability of multi-terminal system.
【学位授予单位】：华北电力大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM721.1

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